US6402703B1 - Dual riser/single capillary viscometer - Google Patents

Abstract

A blood viscosity measuring system and methods for measuring blood viscosity monitors the change in height of one of two, oppositely-moving, columns of blood from the circulating blood of a patient and, given the dimensions of a capillary tube through which the blood flows and by detecting a single blood position of the other oppositely-moving column, determines the blood viscosity over a range of shears, especially low shears. The system includes a tube set (disposable or non-disposable) that includes a pair of riser tubes, a capillary tube of predetermined dimensions that is coupled between the riser tubes (or that forms a portion of one riser tube) and a valve mechanism for controlling the circulating flow of blood from the patient into the riser tubes. A sensor monitors the movement of one of the columns of blood in one of the riser tubes and a single point detector detects a single blood position of the other column of blood and an associated microprocessor analyzes this movement and single point, along with the predetermined dimensions of the capillary tube, to determine the viscosity of the patient's circulating blood.

Description

RELATED APPLICATIONS

This application is a Continuation-in-Part of application Ser. No. 09/439,795, filed Nov. 12, 1999, entitled DUAL RISER/SINGLE CAPILLARY VISCOMETER, which in turn is a Continuation-in-Part of application Ser. No. 08/919,906, filed Aug. 28, 1997 (now U.S. Pat. No. 6,019,735, issued on Feb. 1, 2000), entitled VISCOSITY MEASURING APPARATUS AND METHOD OF USE, all of which are assigned to the same Assignee as the present invention and all of whose entire disclosures are incorporated by reference herein.

BACKGROUND OF THE INVENTION

This invention relates generally to an apparatus and method for measuring the viscosity of liquids, and more particularly, an apparatus and methods for measuring the viscosity of the blood of a living being in-vivo and over a wide range of shears.

The importance of determining the viscosity of blood is well-known.Fibrogen, Viscosity and White Blood Cell Count Are Major Risk Factors for Ischemic Heart Disease, by Yarnell et al., Circulation, Vol. 83, No. 3, March 1991; Postprandial Changes in Plasma and Serum Viscosity and Plasma Lipids and Lipoproteins After an Acute Test Meal, by Tangney, et al., American Journal for Clinical Nutrition, 65:36-40, 1997; Studies of Plasma Viscosity in Primary Hyperlipoproteinaemia, by Leonhardt et al., Atherosclerosis 28, 29-40, 1977; Effects of Lipoproteins on Plasma Viscosity, by Seplowitz,t al., Atherosclerosis 38, 89-95, 1981; Hyperviscosity Syndrome in a Hypercholesterolemic Patient with Primary Biliary Cirrhosis, Rosenson, et al., Gastroenterology, Vol. 98, No. 5, 1990; Blood Viscosity and Risk of Cardiovascular Events:the Edinburgh Artery Study, by Lowe et al., British Journal of Hematology, 96, 168-171,1997; Blood Rheology Associated with Cardiovascular Risk Factors and Chronic Cardiovascular Diseases: Results of an Epidemiologic Cross-Sectional Study, by Koenig, et al., Angiology, The Journal of Vascular Diseases, November 1988; Importance of Blood Viscoelasticity in Arteriosclerosis, by Hell, et al., Angiology, The Journal of Vascular Diseases, June, 1989; Thermal Method for Continuous Blood-Velocity Measurements in Large Blood Vessels, and Cardiac-Output Determination, by Delanois, Medical and Biological Engineering, Vol. 11, No. 2, March 1973; Fluid Mechanics in Atherosclerosis, by Nerem, et al., Handbook of Bioengineering,Chapter 21, 1985.

Much effort has been made to develop apparatus and methods for determining the viscosity of blood.Theory and Design of Disposable Clinical Blood Viscometer, by Litt et al., Biorheology, 25, 697-712, 1988; Automated Measurement of Plasma Viscosity by Capillary Viscometer, by Cooke, et al., Journal of Clinical Pathology 41, 1213-1216, 1988; A Novel Computerized Viscometer/Rheometerby Jimenez and Kostic, Rev. Scientific Instruments 65,Vol 1, January 1994; A New Instrument for the Measurement of Plasma-Viscosity, by John Harkness, The Lancet, pp. 280-281, Aug. 10, 1963; Blood Viscosity and Raynaud's Disease, by Pringle, et al., The Lancet, pp. 1086-1089, May 22, 1965; Measurement of Blood Viscosity Using a Conicylindrical Viscometer, by Walker et al., Medical and Biological Engineering, pp. 551-557, September 1976.

One reference, namely,The Goldman Algorithm Revisited: Prospective Evaluation of a Computer-Derived Algorithm Versus Unaided Physician Judgment in Suspected Acute Myocardial Infarction, by Qamar, et al., Am Heart J 138(4):705-709, 1999, discusses the use of the Goldman algorithm for providing an indicator to acute myocardial infarction. The Goldman algorithm basically utilizes facts from a patient's history, physical examination and admission (emergency room) electrocardiogram to provide an AMI indicator.

In addition, there are a number of patents relating to blood viscosity measuring apparatus and methods. See for example, U.S. Pat. No.: 3,342,063 (Smythe et al.); U.S. Pat. No. 3,720,097 (Kron); U.S. Pat. No. 3,999,538 (Philpot, Jr.); U.S. Pat. No. 4,083,363 (Philpot); U.S. Pat. No. 4,149,405 (Ringrose); U.S. Pat. No. 4,165,632 (Weber, et. al.); U.S. Pat. No. 4,517,830 (Gunn, deceased, et. al.); U.S. Pat. No. 4,519,239 (Kiesewetter, et. al.); U.S. Pat. No. 4,554,821 (Kiesewetter, et. al.); U.S. Pat. No. 4,858,127 (Kron, et. al.); U.S. Pat. No. 4,884,577 (Merrill); U.S. Pat. No. 4,947,678 (Hori et al.); U.S. Pat. No. 5,181,415 (Esvan et al.); U.S. Pat. No. 5,257,529 (Taniguchi et al.); U.S. Pat. No. 5,271,398 (Schlain et al.); and U.S. Pat. No. 5,447,440 (Davis, et. al.).

The Smythe '063 patent discloses an apparatus for measuring the viscosity of a blood sample based on the pressure detected in a conduit containing the blood sample. The Kron '097 patent discloses a method and apparatus for determining the blood viscosity using a flowmeter, a pressure source and a pressure transducer. The Philpot '538 patent discloses a method of determining blood viscosity by withdrawing blood from the vein at a constant pressure for a predetermined time period and from the volume of blood withdrawn. The Philpot '363 patent discloses an apparatus for determining blood viscosity using a hollow needle, a means for withdrawing and collecting blood from the vein via the hollow needle, a negative pressure measuring device and a timing device. The Ringrose '405 patent discloses a method for measuring the viscosity of blood by placing a sample of it on a support and directing a beam of light through the sample and then detecting the reflected light while vibrating the support at a given frequency and amplitude. The Weber '632 patent discloses a method and apparatus for determining the fluidity of blood by drawing the blood through a capillary tube measuring cell into a reservoir and then returning the blood back through the tube at a constant flow velocity and with the pressure difference between the ends of the capillary tube being directly related to the blood viscosity. The Gunn '830 patent discloses an apparatus for determining blood viscosity that utilizes a transparent hollow tube, a needle at one end, a plunger at the other end for creating a vacuum to extract a predetermined amount and an apertured weight member that is movable within the tube and is movable by gravity at a rate that is a function of the viscosity of the blood. The Kiesewetter '239 patent discloses an apparatus for determining the flow shear stress of suspensions, principally blood, using a measuring chamber comprised of a passage configuration that simulates the natural microcirculation of capillary passages in a being. The Kiesewetter '821 patent discloses another apparatus for determining the viscosity of fluids, particularly blood, that includes the use of two parallel branches of a flow loop in combination with a flow rate measuring device for measuring the flow in one of the branches for determining the blood viscosity. The Kron '127 patent discloses an apparatus and method for determining blood viscosity of a blood sample over a wide range of shear rates. The Merrill '577 patent discloses an apparatus and method for determining the blood viscosity of a blood sample using a hollow column in fluid communication with a chamber containing a porous bed and means for measuring the blood flow rate within the column. The Hori '678 patent discloses a method for measurement of the viscosity change in blood by disposing a temperature sensor in the blood flow and stimulating the blood so as to cause a viscosity change. The Esvan '415 patent discloses an apparatus that detects the change in viscosity of a blood sample based on the relative slip of a drive element and a driven element, which holds the blood sample, that are rotated. The Taniguchi '529 patent discloses a method and apparatus for determining the viscosity of liquids, e.g., a blood sample, utilizing a pair of vertically-aligned tubes coupled together via fine tubes while using a pressure sensor to measure the change of an internal tube pressure with the passage of time and the change of flow rate of the blood. The Bedingham '328 patent discloses an intravascular blood parameter sensing system that uses a catheter and probe having a plurality of sensors (e.g., an O₂sensor, CO₂sensor, etc.) for measuring particular blood parameters in vivo. The Schlain '398 patent discloses a intra-vessel method and apparatus for detecting undesirable wall effect on blood parameter sensors and for moving such sensors to reduce or eliminate the wall effect. The Davis '440 patent discloses an apparatus for conducting a variety of assays that are responsive to a change in the viscosity of a sample fluid, e.g., blood.

Viscosity measuring methods and devices for fluids in general are well-known. See for example, U.S. Pat. No.: 1,810,992 (Dallwitz-Wegner); U.S. Pat. No. 2,343,061 (Irany); U.S. Pat. No. 2,696,734 (Brunstrum et al.); U.S. Pat. No. 2,700,891 (Shafer); U.S. Pat. No. 2,934,944 (Eolkin); U.S. Pat. No. 3,071,961 (Heigl et al.); U.S. Pat. No. 3,116,630 (Piros); U.S. Pat. No. 3,137,161 (Lewis et al.); U.S. Pat. No. 3,138,950 (Welty et al.); U.S. Pat. No. 3,277,694 (Cannon et al.); U.S. Pat. No. 3,286,511 (Harkness); U.S. Pat. No. 3,435,665 (Tzentis); U.S. Pat. No. 3,520,179 (Reed); U.S. Pat. No. 3,604,247 (Gramain et al.); U.S. Pat. No. 3,666,999 (Moreland, Jr. et al.); U.S. Pat. No. 3,680,362 (Geerdes et al.); U.S. Pat. No. 3,699,804 (Gassmann et al.); U.S. Pat. No. 3,713,328 (Aritomi); U.S. Pat. No. 3,782,173 (Van Vessem et al.); U.S. Pat. No. 3,864,962 (Stark et al.); U.S. Pat. No. 3,908,441 (Virloget); U.S. Pat. No. 3,952,577 (Hayes et al.); U.S. Pat. No. 3,990,295 (Renovanz et al.); U.S. Pat. No. 4,149,405 (Ringrose); U.S. Pat. No. 4,302,965 (Johnson et al.); U.S. Pat. No. 4,426,878 (Price et al.); U.S. Pat. No. 4,432,761 (Dawe); U.S. Pat. No. 4,616,503 (Plungis et al.); U.S. Pat. No. 4,637,250 (Irvine, Jr. et al.); U.S. Pat. No. 4,680,957 (Dodd); U.S. Pat. No. 4,680,958 (Ruelle et al.); U.S. Pat. No. 4,750,351 (Ball); U.S. Pat. No. 4,856,322 (Langrick et al.); U.S. Pat. No. 4,899,575 (Chu et al.); U.S. Pat. No. 5,142,899 (Park et al.); U.S. Pat. No. 5,222,497 (Ono); U.S. Pat. No. 5,224,375 (You et al.); U.S. Pat. No. 5,257,529 (Taniguchi et al.); U.S. Pat. No. 5,327,778 (Park); and U.S. Pat. No. 5,365,776 (Lehmann et al.).

The following U.S. patents disclose viscosity or flow measuring devices, or liquid level detecting devices using optical monitoring: U.S. Pat. No. 3,908,441 (Virloget); U.S. Pat. No. 5,099,698 (Kath, et. al.); U.S. Pat. No. 5,333,497 (Br nd Dag A. et al.). The Virloget '441 patent discloses a device for use in viscometer that detects the level of a liquid in a transparent tube using photodetection. The Kath '698 patent discloses an apparatus for optically scanning a rotameter flow gauge and determining the position of a float therein. The Br nd Dag A. '497 patent discloses a method and apparatus for continuous measurement of liquid flow velocity of two risers by a charge coupled device (CCD) sensor.

U.S. Pat. No. 5,421,328 (Bedingham) discloses an intravascular blood parameter sensing system.

A statutory invention registration, H93 (Matta et al.) discloses an apparatus and method for measuring elongational viscosity of a test fluid using a movie or video camera to monitor a drop of the fluid under test.

The following publications discuss red blood cell deformability and/or devices used for determining such:Measurement of Human Red Blood Cell Deformability Using a Single Micropore on a Thin Si₃N₄Film, by Ogura et al, IEEE Transactions on Biomedical Engineering, Vol. 38, No. 8, August 1991; the Pall BPF4High Efficiency Leukocyte Removal Blood Processing Filter System, Pall Biomedical Products Corporation, 1993.

A device called the “Hevimet 40” has recently been advertised at www.hevimet.freeserve.co.uk. The Hevimet 40 device is stated to be a whole blood and plasma viscometer that tracks the meniscus of a blood sample that falls due to gravity through a capillary. While the Hevimet 40 device may be generally suitable for some whole blood or blood plasma viscosity determinations, it appears to exhibit several significant drawbacks. For example, among other things, the Hevimet 40 device appears to require the use of anti-coagulants. Moreover, this device relies on the assumption that the circulatory characteristics of the blood sample are for a period of 3 hours the same as that for the patient's circulating blood. That assumption may not be completely valid.

Notwithstanding the existence of the foregoing technology, a need remains for an apparatus and method for obtaining the viscosity of the blood of a living being in-vivo and over a range of shears and for the provision of such data in a short time span.

OBJECTS OF THE INVENTION

Accordingly, it is the general object of the instant invention to provide an apparatus and methods for meeting that need.

It is a further object of this invention to provide viscosity measuring an apparatus and methods for determining the viscosity of circulating blood over a range of shear rates, especially at low shear rates.

It is still yet a further object of this invention to provide an apparatus and methods for determining viscosity of the circulating blood of a living being (e.g., in-vivo blood viscosity measurement) without the need to directly measure pressure, flow and volume.

It is yet another object of this invention to provide an indication of the viscosity of the circulating blood of a living being in a short span of time.

It is yet another object of this invention to provide an apparatus and methods for measuring the viscosity of the circulating blood of a living being and with minimal invasiveness.

It is still yet another object of the present invention to provide an apparatus and methods for measuring the viscosity of the circulating blood of a living being that does not require the use of anti-coagulants, or other chemicals or biologically active materials.

It is still yet even another object of the present invention to provide an apparatus and method for measuring the viscosity of blood of a living being that does not require the blood to be exposed to atmosphere or oxygen.

It is still yet another object of the present invention to provide an apparatus and method for determining the viscosity of the circulating blood contemporaneous with the diversion of the blood into a conveying means (e.g., needle) when that means is coupled to, e.g., inserted into, the patient.

It is still yet another object of the present invention to provide an apparatus and methods for measuring the circulating blood viscosity of a living being that comprises disposable portions for maintaining a sterile environment, ease of use and repeat testing.

It is still yet another object of the present invention to provide a blood viscosity measuring apparatus and methods for determining the thixotropic point of the blood.

It is even yet another object of the present invention to provide an apparatus and methods for determining the yield stress of the circulating blood.

It is moreover another object of the present invention to provide an apparatus and methods for detecting circulating blood viscosity to evaluate the efficacy of pharmaceuticals, etc., to alter blood viscosity of the circulating blood of a living being.

It is even yet another object of this invention to provide an apparatus and methods for detecting the viscosity of the circulating blood of a patient while negating the effects of venous pressure.

SUMMARY OF THE INVENTION

In accordance with one aspect of this invention an apparatus is provided for effecting the viscosity measurement (e.g., in real-time) of circulating blood in a living being. The apparatus comprises: a lumen arranged to be coupled to the vascular system of the being; a pair of tubes having respective first ends coupled to the lumen for receipt of circulating blood from the being, and wherein one of the pair of tubes comprises a capillary tube having some known parameters; a valve for controlling the flow of circulating blood from the being's vascular system to the pair of tubes; and an analyzer, coupled to the valve, for controlling the valve to permit the flow of blood into the pair of tubes whereupon the blood in each of the pair of tubes assumes a respective initial position with respect thereto. The analyzer is also arranged for operating the valve to isolate the pair of tubes from the being's vascular system and for coupling the pair of tubes together so that the position of the blood in the pair of tubes changes. The analyzer is also arranged for monitoring the blood position change in one of the tubes and detecting a single blood position in the other one of the pair of tubes and calculating the viscosity based thereon.

In accordance with another aspect of this invention a method is provided for determining the viscosity (e.g., in real-time) of circulating blood of a living being. The method comprises the steps of: (a) providing access to the circulating blood of the living being to establish an input flow of circulating blood; (b) dividing the input flow of circulating blood into a first flow path and a second flow path into which respective portions of the input flow pass and wherein one of the first or second flow paths includes a passageway portion having some known parameters; (c) isolating the first and second flow paths from the input flow and coupling the first and second flow paths together so that the position of the blood in each of the flow paths changes; (d) monitoring the blood position change in one of the first and second flow paths over time; (e) detecting as single blood position in the other one of said first and second flow paths; and (f) calculating the viscosity of the circulating blood based on the blood position change, the single blood position and on selected known parameters of the passageway portion.

In accordance with still another aspect of this invention an apparatus is provided for effecting the viscosity measurement (e.g., in real-time) of circulating blood in a living being. The apparatus comprises: a lumen arranged to be coupled to the vascular system of the being; a pair of tubes having respective first ends and second ends wherein the first ends are coupled together via a capillary tube having some known parameters; a valve for controlling the flow of circulating blood from the being's vascular system to the pair of tubes wherein the valve is coupled to a second end of one of the pair of tubes and is coupled to the lumen; and an analyzer, coupled to the valve, for controlling the valve to permit the flow of blood into the pair of tubes whereupon the blood in each of the pair of tubes assumes a respective initial position with respect thereto. The analyzer also is arranged for operating the valve to isolate the pair of tubes from the being's vascular system so that the position of the blood in the pair of tubes changes. The analyzer also is arranged for monitoring the blood position change in one of the tubes and detecting a single blood position in the other one of the pair of tubes and calculating the viscosity of the blood based thereon.

In accordance with yet another aspect of this invention a method is provided for determining the viscosity (e.g., in real-time) of circulating blood of a living being. The method comprises the steps of: (a) providing access to the circulating blood of the living being to form an input flow of circulating blood; (b) directing the input flow into one end of a pair of tubes coupled together via a passageway having some known parameters whereby the input flow passes through a first one of the pair of tubes, through the passageway and into a first portion of a second one of the pair of tubes in order to form respective columns in the first and second tubes; (c) isolating the respective columns from the input flow so that the position of the blood in each of the columns changes; (d) monitoring the blood position change in one of the columns of blood over time; (e) detecting a single blood position in the other one of the pair of tubes; and (f) calculating the viscosity of the circulating blood based on the blood position change, the single blood position and on selected known parameters of the passageway.

DESCRIPTION OF THE DRAWINGS

Other objects and many of the intended advantages of this invention will be readily appreciated when the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:

FIG. 1 is a block diagram of the dual riser/single capillary (DRSC) viscometer;

FIG. 2 is a front view of one embodiment of the DRSC viscometer depicting the respective housings for the blood receiving means, with its door opened, and the analyzer/output portion;

FIG. 3 is a side view of the embodiment of FIG. 2;

FIG. 4 is a functional diagram of the DRSC viscometer just prior to making a viscosity test run;

FIG. 5 is a functional diagram of the DRSC viscometer during the viscosity test run;

FIG. 6 depicts a graphical representation of the respective columns of fluid in the riser tubes of the DRSC viscometer during the viscosity test run;

FIGS. 7A-7C depict the operation of the valve mechanism of the DRSC viscometer just prior to, and during, the viscosity test run;

FIG. 8 is a block diagram for the DRSC viscometer which detects movement of the column of fluid in either of the riser tubes using various types of sensors;

FIGS. 9A-9B comprise a flow chart of the operation of the DRSC viscometer;

FIG. 10A depicts a graphical representation of the viscosity of a living patient's circulating blood plotted for a range of shear rates;

FIG. 10B depicts a graphical representation of the logarithm of the viscosity of a living patient's circulating blood plotted against the logarithm of shear rates;

FIG. 11 depicts an implementation of the capillary and riser tube portion of the blood receiving means;

FIG. 12 is a partial cross-sectional view taken alongline12—12 of FIG.11.

FIG. 13 is a block diagram of a second more preferred dual riser/single capillary (DRSC) viscometer;

FIG. 14 is a front view of the second embodiment of the DRSC viscometer depicting the respective housings for the blood receiving means, with its door opened, and the analyzer/output portion;

FIG. 15 is a functional diagram of the second embodiment of the DRSC viscometer just prior to making a viscosity test run;

FIG. 16 is a functional diagram of the second embodiment of the DRSC viscometer during the viscosity test run;

FIGS. 17A-17C depict the operation of the valve mechanism of the second embodiment of the DRSC viscometer just prior to, and during, the viscosity test run;

FIG. 18 is a block diagram for the second embodiment of the DRSC viscometer which detects movement of the column of fluid in each of the riser tubes using various types of sensors;

FIGS. 19A-19B comprise a flow chart of the operation of the second embodiment of the DRSC viscometer;

FIG. 20 depicts an implementation of the capillary and riser tube portion of the blood receiving means for the second embodiment of the DRSC viscometer; and

FIG. 21 is a partial cross-sectional view taken alongline21—21 of FIG.20.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

As stated previously, the present application is a Continuation-in-Part of Co-Pending application Ser. No. 09/439,795, filed Nov. 12, 1999, entitled DUAL RISER/SINGLE CAPILLARY VISCOMETER, which in turn is a Continuation-in-Part of application Ser. No. 08/919,906 filed Aug. 28, 1997 (now U.S. Pat. No. 6,019,735), entitled VISCOSITY MEASURING APPARATUS AND METHOD OF USE, assigned to the same Assignee as the present invention and all of whose entire disclosures are incorporated by reference herein. For measuring the viscosity of circulating blood, including whole blood, of a living being, the apparatus and method as disclosed in U.S. Pat. No. 6,019,735 are generally preferable. To negate venous pressure effects at low shear rates, cuffing the living being, or other suitable means, may be used with that apparatus and method.

An alternative apparatus and method of the present invention to negate pressure at low shear rates for measuring the viscosity of circulating blood, including whole blood, of a living being is shown generally at920 in FIG.1. The dual riser/single capillary (DRSC)viscometer920 basically comprises a blood receiving means22 and an analyzer/output portion924. The analyzer/output portion924 is similar to the analyzer output portion24 of application Ser. No. 09/439,795, except that one of the column level detectors, e.g., column level detector54 for riser tube R1, is replaced with asingle point detector954, as will be discussed in detail later. Suffice it to say for now, that theapparatus920 is similar in structure and operation to the apparatus20 except for the substitution of one of the column level detectors with asingle point detector954.

The patient is coupled to theDRSC viscometer920 through a circulatingblood conveying means26, e.g., a needle, an IV needle, an in-dwelling catheter, etc., or any equivalent structure that can convey circulating blood from a patient to the DRSC viscometer20. As will be discussed in detail later, the analyzer/output portion924 provides adisplay28 for presenting the viscosity information, as well as other information to the operator. The analyzer/output portion924 may also provide this information to other suitable output means30, such as adatalogger32, other computer(s)34, aprinter36, aplotter38, remote computers/storage40, to the Internet42 or to other on-line services44.

The blood receiving means22 basically comprises avalve mechanism46 coupled to a first riser tube R1 on one side and coupled to a second riser tube R2 via acapillary tube52 on the other side. Thecapillary tube52 is of small uniform inside diameter, e.g., 60 mm-length, 0.8 mm inside diameter. When the circulating blood conveying means26 (hereinafter the “CBCM26”) is coupled to the blood receiving means22, thevalve mechanism46 controls the flow of blood into the receiving means22, as will be discussed in detail later. Each of the riser tubes R1 and R2 are preferably the same dimensions (e.g., 12 inch long, 2 mm inside diameter).

It should be understood that the blood receiving means22 may be disposable or non-disposable. As will be discussed in detail later, where the blood receiving means22 are disposable, the components (valve mechanism46, riser tubes R1 and R2 and capillary tube52) are releasably secured in a blood receiving means housing that can be quickly and easily inserted, used during the viscosity test run and then quickly and easily removed for disposal; another disposable blood receiving means22 is then inserted in preparation for the next viscosity test run. On the other hand, where the blood receiving means22 is non-disposable, the components (valve mechanism46, riser tubes R1 and R2 and capillary tube52) can be thoroughly washed and cleaned in place in preparation for the next viscosity test run.

It should be understood that thecapillary tube52 does not necessarily have to be an elongated tube but may comprise a variety of configurations such as a coiled capillary tube.

As mentioned earlier, the analyzer/output portion924 differs from the analyzer/output portion24 of application Ser. No. 09/439,795 in that the analyzer/output portion924 comprises only a singlecolumn level detector56 and asingle point detector954. This modification to the analyzer/output portion24 of application Ser. No. 09/439,795 is based on the symmetry of the column of blood height (i.e., h₁(t) and h₂(t)) vs. time data (see FIG.6). As long as one of the two columns ofblood82/84 is monitored, the height vs. time data for the other column of blood can be generated by using a single height point from that column. In the invention of the present application, it is only necessary to monitor the change in position of one of the columns of blood in either riser tube R1 or riser tube R2 and to detect only one point from the other column of blood. The preferred method/means is to monitor the rising column ofblood84 which occurs in riser tube R2 and to detect the initial viscosity test run level (i.e., h_1i, as will be discussed in detail later) of the column ofblood82 in riser tube R1. Thus, it is within the broadest scope of this invention to cover a monitor that monitors either one of the moving columns of blood but not both (as is disclosed in application Ser. No. 09/439,795) and a single point detector for detecting one point from the other moving column of blood.

In particular, the analyzer/output portion924 basically comprises the singlecolumn level detector56, thesingle point detector954, aprocessor58, thedisplay28, abar code reader78, anenvironmental control unit80, and a first battery B1 and a second back-up battery B2. The column level detector56 (comprising an LED (light emitting diode)array64 and a CCD (charge coupled device)66, as will be discussed in detail later) monitors the rising level of blood in the second riser tube R2; furthermore, thesingle point detector954, may comprise (but is not limited to) anLED964 and aphotodetector966, which detect a specific level of the column of blood, e.g., h_1i, as will also be discussed in detail later.

The processor58 (e.g., a “386” microprocessor or greater, or any equivalent) is arranged to analyze the data from thedetector56 and calculate the blood viscosity therefrom, as will also be discussed in detail later. Furthermore, theprocessor58 also controls thedisplay28 for providing the viscosity information and the other information to the operator as well as to the other output means30. Theprocessor58 also controls thevalve mechanism46 based on the data from thedetector56, as will be discussed later. Battery B1 provides all of the requisite power to the analyzer/output portion924, with battery B2 serving as a back-up power supply. Thebar code reader78 and theenvironmental control unit80 will be described later.

As shown more clearly in FIGS. 2-3, theDRSC viscometer920 comprises the blood receiving means22 and the analyzer/output portion924 contained inrespective housings60 and62, each of which can be releasably secured to a common frame, e.g., a conventional intravenous (IV)pole48. In this configuration, the analyzer/output portion924 can be positioned in an inclined orientation (see FIG. 3) to facilitate user operation and viewing of thedisplay28. However, it should be understood that the respective housing constructions are exemplary, and others can be incorporated without limiting the scope of this invention.

Thedisplay28 may comprise any suitable conventional devices, e.g., an ELD (electroluminescent display) or LCD (liquid crystal display) that permits the visualization of both text and graphics. The resolution of thisdisplay28 is preferably 800×600 VGA or above. Furthermore, while the preferred embodiment utilizes a touch screen display which incorporates, among other things:

graphical display61

instruction, and/or data, display65 (which also includes the command line display shown as “RUN TEST”; e.g., “TESTING”, “TEST IN PROGRESS,” etc.)

alphanumeric keypad68

emergency stop button70

battery status indicators,72A and72B

function buttons74,

it should be understood that any equivalent display device is within the broadest scope of the invention. Thus, any number of user interfaces and buttons may be available through thedisplay28. Therefore theinvention920 is not limited to the embodiment that is shown in FIG.2. Moreover, thedisplay28 can be operated to minimize or maximize, or overlay any particular graphic or text screen, as is available in any conventional object-oriented operating system, such as Microsoft® WINDOWS.

Thelower housing60 comprises the blood receiving means22 and thecolumn level detector56. In the preferred embodiment, thecolumn level detector56 comprises an LED (light emitting diode)array64 and a CCD (charge coupled device)66 located on opposite sides of the riser tube R2. When thecolumn level detector56 is operating, eachLED array64 illuminates the riser tube R2, and depending on whether there is fluid in the column, various pixels in theCCD66 will either detect the light from the LED array64 (no fluid in the column, thereby permitting the light to pass through the riser tube) or not (fluid is present and is blocking the passage of light from the LED array64). The pixel data of eachCCD66 is passed to the analyzer/output924 through conventional wire harnesses (not shown) for use by theprocessor58. Furthermore, power for theLED arrays64 and theCCDs66 is provided via these wire harnesses from the batteries B1/B2, if the batteries are contained in the analyzer/output housing62.

With respect to thesingle point detector954, during operation of theapparatus920, with thevalve mechanism46 open, blood flows up the riser tube R1 while thephotodetector966 continues to detect the light from theLED964. Once the top of the column ofblood82 interrupts the light from theLED964, thephotodetector966 informs theprocessor58, which operates thevalve mechanism46, to halt any further blood flow into riser tube R1. This level of the column of blood defined as h_1i, forms the initial starting point of the column of blood in riser tube R1 for the viscosity test run, i.e., the column of blood in riser tube R1 falls away from this level h_1iwhen the viscosity test begins. Since the position of thephotodetector966 is at the predetermined location, h_1i, above the reference level (FIG.2), thephotodetector966 acts to verify that the initial position, h_1ihas been reached by the column of blood in riser tube R1.

Alternatively, as mentioned earlier, thecolumn level detector56 can be used to detect the falling column of blood in the first riser tube R1 and thesingle point detector954 can be used to detect the initial viscosity test run position, h_2i, of the rising column of blood in riser tube R2. Thus, it is within the broadest scope of the invention to cover the use of one column level detector for monitoring the change in position of the blood column in one riser tube and the use of a single point detector for detecting a single point of the blood column in the other riser tube.

It should be understood that any one point of the blood column can be detected by thesingle point detector954. The preferred point is the initial column level for the viscosity test run, namely h_1ior h_2i. However, any other point in the column can be detected in order to generate the corresponding height vs. time data/curve.

Where the blood receiving means22 is disposable, it is releasably secured in thehousing60 such that once a test run is completed and/or a new patient is to be tested, all of the lumens (e.g., the tube50, the capillary52, the riser tubes R1 an R2 and the valve mechanism46) can be easily/quickly removed, disposed of and a new set inserted. For example, brackets47 (FIG. 2) may be used to releasably secure the upper portions of the riser tubes R1 and R2 and the lower portions of the riser tubes R1 and R2; thevalve mechanism46 comprises aport49 that fits snugly into an opening (not shown) in the bottom wall of thehousing60. Thecolumn level detector56 is preferably not removable from thehousing60. A door76 (which can be vertically or horizontally hinged to the housing60) is provided to establish a darkened environment during the test run. Thedoor76 also supports thebar code reader78, mentioned earlier. Thisbar code reader78 automatically reads a bar code (not shown) that is provided on one of the riser tubes (e.g., R2). The bar code contains all of the predetermined data regarding the characteristics of the capillary tube52 (e.g., its length and diameter) and the characteristics of the riser tubes R1 and R2. This information is passed to theprocessor58 which is then used to determine the viscosity, as will be discussed in detail later. Thebar code reader78 passes this information to theprocessor58 via the wire harnesses discussed earlier. It should be understood that the location (on the door76) of thebar code reader78 is exemplary only and that other locations within the unit are encompassed by the scope of the invention.

It should be understood that thebrackets47 do not interfere in any way with the column level monitoring, nor the single point detection, since the movement of blood in the riser tubes R1/R2 that is being monitored/detected during the viscosity test run is in between the upper andlower bracket47 pairs.

Thedoor76 also supports an environmental control unit80 (e.g., a heater, fan and/or thermostat) such that when it is closed in preparation for the test, thecapillary tube52 is then heated (or cooled) and maintained throughout the test run at the same temperature and environment as the patient. Prior to the run, the patient's temperature is taken and the operator enters this temperature (via the touch screen display28). Theenvironmental control unit80 then operates to achieve and maintain this temperature. It should be noted that it is within the broadest scope of this invention to include aenvironmental control unit80 that achieves and maintains the entire blood receiving means22 at the patient's temperature during the run. Power to thebar code reader78 andtemperature control unit80 is provided by the analyzer/output924 through the wire harnesses (not shown) discussed previously.

One exemplary implementation of the blood receiving means22 is shown in FIGS. 11-12. In particular, the riser tubes R1 and R2 (e.g., injection-molded pieces) haveintegral elbows50A and50B that are inserted into respective ports (not shown) of the valve mechanism46 (e.g., a single, 3-way stop cock valve). Prior to inserting theelbow portion50B of riser R2 into its corresponding valve mechanism port, acapillary insert53 havinginternal capillary52, is positioned inside the riser tube R2. As shown most clearly in FIG. 12, thecapillary insert53 comprises a taperedentry port55 and atapered exit port57 to minimize any turbulence as the circulating blood passes from the valve mechanism through theelbow50B and up into riser tube R2.

The batteries B1/B2 may comprise a 12VDC, 4 amp-hour batteries, or any equivalent power supply (e.g., batteries used in conventional lap-top computers such as lithium ion batteries). Thedisplay28 provides thestatus indicators72A/72B for each battery in the DRSC viscometer20. In particular, when the DRSC viscometer20 is operating off of battery B1, the twobattery indicators72A/72B appear on thedisplay28. However, once battery B1 is depleted, thebattery B1 indicator72A disappears and thebattery B2 indicator72B blinks to warn the operator that the DRSC viscometer20 is now operating off of the back-up battery B2 and re-charge of battery B1 is necessary.

The concept of viscosity determination using theDRSC viscometer920 is to monitor the change in height of one of two, oppositely-moving, columns of blood from the circulating blood of a patient and given the dimensions of a capillary through which one of the columns of blood must flow. TheDRSC viscometer920 accomplishes this by operating thevalve mechanism46 to first establish an optimum separation distance between the two columns ofblood82 and84 in the respective riser tubes R1 and R2 (FIG.4). Once established, the DRSC viscometer20, via itsvalve mechanism46, couples these two columns ofblood82/84 together and permits them to reach equilibrium while monitoring the movement of the twocolumns blood82/84 (FIG.5).

In particular, as shown in FIG. 4, continuous blood flow from the patient is permitted to flow from theCBCM26, through thevalve mechanism46, and into both riser tubes R1 and R2. During this flow, thecolumn level detector56 monitors the height of the rising column of blood. When the optimum separation distance is achieved, i.e., when the column of blood in riser tube R1 reaches h_1iand the column of blood in riser tube R2 reaches h_2i, thevalve mechanism46 stops the flow of blood from theCBCM26 and simultaneously couples the columns of blood together (FIG.5). As a result, the column of blood in riser R1 falls and the column of blood in riser R2 climbs toward a final equilibrium value, h_∞ (which, as will be discussed later, is actually an offset known as “Δh”). It is the detection of one (preferably the rising column in riser tube R2) of these oppositely moving columns of blood (FIG.5), which is important for blood viscosity determination, as will be discussed later. The graphical representation of h₁(t) and h₂(t) is shown in FIG.6.

It should be understood that the optimum separation distance, i.e., h_1i−h_2i, as well as the dimensions of thecapillary tube52, avoids any oscillations of the columns of blood at the end of the viscosity test run. In other words, these two factors provide for the flat appearance of each of the plots h₁(t) and h₂(t) at the end of the viscosity test run, as shown in FIG.6.

FIGS. 7A-7C depict a typical sequence of how thevalve mechanism46 establishes the pre-test run columns of blood (FIG. 4) and the test run columns of blood (FIG.5). Thevalve mechanism46 comprises a single, 3-way stop cock valve. The valve may comprise a solenoid (e.g., 500 mA solenoid, or stepper motor, etc., indicated by valve driver86) that is pulsed by theprocessor58 to operate the valve in the appropriate direction. In particular, theprocessor58 commands rotation of the valve by issuing a positive or negative pulse to the solenoid. For example, to receive patient circulating blood flow into theDRSC viscometer920 initially, thevalve driver86 configures the valve to allow circulating blood to enter both riser tubes R1 and R2 through respective tubing13 and14 (FIG.7A). Thecolumn level detector56 is monitoring the rising column ofblood84 during this time. Should the column of blood pre-test level h_1i, be reached first, theprocessor58 issues a positive pulse to thevalve driver86 to close off flow to riser tube R1 (FIG.7B); alternatively, should the column of blood pre-test level h_2ibe reached first, theprocessor58 issues a negative pulse to close off flow to riser tube R2 while continuing to allow is circulating blood flow into riser tube R1 (not shown). Finally, to couple the two riser tubes R1 and R2 together while isolating them from the circulating blood flow of the patient, theprocessor58 commands thevalve driver86 to the position shown in FIG.7C.

As shown in FIG. 8, it is within the broadest scope of the invention to include any means and/or method for monitoring the movement of either one of the columns ofblood82/84 in the riser tubes R1/R2 and for detecting the single point in the other one of the columns and, as such, are not limited to theLED array64/CCD66 arrangement for thecolumn level detector56, nor to theLED964/photodetector966 arrangement for thesingle point detector954. In fact, the following type of physical detections (indicated by “SENSOR” in FIG. 8) are covered by the present invention:

d(Weight)/dt: the change in weight of either column of fluid with respect to time using a weight detecting means for either column of fluid as the sensor; e.g., w₁(t)−w₂(t);

d(Pressure)/dt: the change in pressure of either column of fluid with respect to time using a pressure transducer located at the top of either column of fluid; e.g., p₁(t)−p₂(t);

time of flight: the length of time it takes an acoustic signal to be emitted from a sensor (e.g., ultrasonic) located above either column of fluid and to be reflected and return to the sensor; e.g., time of flight₁(t)−time of flight₂(t);

d(Volume)/dt: the change in volume of either column of fluid with respect to time; e.g., V₁(t)−V₂(t);

d(Position)/dt: the change in position of either column level using a digital video camera; e.g., Pos₁(t)−Pos₂(t);

d(Mass)/dt: the change in mass with respect to time for either column of fluid; e.g., m₁(t)−m₂(t).

FIGS. 9A-9B comprise a flowchart of the detailed operation of theDRSC viscometer920 to determine the viscosity of a patient's circulating blood flow. The overall time of the test run is approximately 3 minutes with theCCD66. When the pixel values of theCCD66 are no longer changing, the DRSC20 determines that Δh has been reached and the test run is terminated.

As discussed earlier, the concept of viscosity determination using theDRSC viscometer920 is to monitor the change in height of one of two, oppositely-moving, columns of blood from the circulating blood of a patient, along with detecting a single point from the other one of the two columns, and given the dimensions of a capillary through which one of the columns of blood must flow.

As stated in application Ser. No. 09/439,795, there are a plurality of mathematical models that can be used as curve fitting models for the data obtained from theviscometers920 and1020, such as a power law model, a Casson model, a Carreau model, a Herschel-Bulkley model, a Powell-Eyring model, a Cross model, Carreau-Yasuda model. It is within the broadest scope of this invention to include all of these models. The following discussion utilizes a power law model and is used by way of example only and not by way of limitation. Thus, one skilled in the art could substitute any of the above curve fitting models for the exemplary power law model discussed below

In particular, for non-Newtonian fluids, as is blood, the viscosity varies with shear rate, however, Hagen-Poiseuille flow within the capillary still holds for steady or quasi-steady laminar flow. For a fluid that is well-correlated with a non-Newtonian power law viscosity model, the capillary pressure drop and flow rate are related as follows:$\begin{array}{cc}\Delta P_c=\frac{4{\mathrm{kL}}_c{\stackrel{.}{\gamma }}^n}{{\phi }_c}=\frac{4{\mathrm{kL}}_c}{{\phi }_c}{\left(\frac{3n+1}{n}\right)\frac{8Q}{{\mathrm{\pi \phi }}_c^3}}^n& \left(1\right)\end{array}$

where the shear rate, {dot over (γ)} is related to the capillary flow rate by:$\begin{array}{cc}\stackrel{.}{\gamma }=\left(\frac{3n+1}{n}\right)\frac{8Q}{{\mathrm{\pi \phi }}_c^3}& \left(2\right)\end{array}$

where the power law viscosity is defined as:

μ=k|{dot over (γ)}|ⁿ⁻¹  (3)

and where

ΔP_c=capillary tube pressure drop (Pa)

L_c=length of capillary tube (m)

Q=volumetric flow rate (m³/s)

k=consistency index (a constant used in capillary viscometry)—that is determined;

n=power law index (another constant used in capillary viscometry)—that is determined;

φ_c=capillary tube diameter (m)

μ=fluid viscosity (centipoise, CP)

{dot over (γ)}=shear rate (s⁻¹)

Since blood, a non-Newtonian fluid, is well-characterized with a power law viscosity model, Equation (1) can be re-written as:$\begin{array}{cc}\rho g\left(h_1-h_2\right)=\frac{4{\mathrm{kL}}_c}{{\phi }_c}{\left\{2\left(\frac{3n+1}{n}\right)·\left(\frac{{\mathrm{<figure-callout\; label="\phi \; r"\; filenames="US06402703-20020611-D00001.png,US06402703-20020611-D00008.png"\; state="\{\{state\}\}">\phi </figure-callout>}}_r^{}}{{\phi }_c^3}\right)\left(\frac{h}{t}\right)\right\}}^n+\Delta h\rho g& \left(4\right)\end{array}$

where

ρ=blood fluid density;

g=gravitational constant;

h₁=instantaneous height of the column of blood in riser R1

h₂=instantaneous height of the column of blood in riser R2

φ_c=inside diameter of the capillary tube

φ_r=inside diameter of riser tube and where φ_c<<<φ_r

Δh=an offset due to yield stress of the blood and is a property of blood.

It should be noted that the length of the capillary tube L_cis assumed large such that any friction forces in the riser tubes R1 and R2 and connecting fluid components can be ignored. In addition, the diameter of the riser tubes R1 and R2 are equal.

By integrating both sides of Equation (4) with respect to time, the need to determine$\frac{h}{t}$

is eliminated, which yields:$\begin{array}{cc}{h}_1-h_2-\Delta h=-{\left\{\left(\frac{n-1}{n}\right)\alpha t+{\left(\Delta h-h_0\right)}^{\frac{n-1}{n}}\right\}}^{\frac{n}{n-1}}& \left(5\right)\end{array}$

where

h₀=h₁(t)−h₂(t) at t=0; i.e., h₀=h_1i−h_2i; and$\begin{array}{cc}\alpha =-\frac{1}{2}{\left(\frac{4{\mathrm{kL}}_c}{\rho g{\phi }_c}\right)}^n\left(\frac{n}{3n+1}\right)\left(\frac{{\phi }_c^3}{{\phi }_r^2}\right)& \left(6\right)\end{array}$

In order to determine the viscosity, it is necessary to determine the values for k and n using curve fitting based on the test run data. In particular, the following procedure is used:

1) Conduct a test run and obtain all h₁(t) and h₂(t) data;

2) Fit curves through the data to obtain symbolic expressions for h₁(t) and h₂(t);

3) Determine all h₁(t)−h₂(t) data, as well as Δh;

3) Assume values for the power law parameters k and n;

4) Calculate the following error values for all data points:$\begin{array}{cc}\mathrm{Error}=\left(h_1-h_2-\Delta h\right)-{\left\{\left(\frac{n-1}{n}\right)\alpha t+{\left(\Delta h-h_0\right)}^{\frac{n-1}{n}}\right\}}^{\frac{n}{n-1}}& \left(7\right)\end{array}$

6) Sum the error values for all data points;

7) Iterate to determine the values of k and n that minimize the error sum; and

8) Use the determined k and n values in Equations (2) and (3) to calculate viscosity. FIG. 10A depicts a graphical representation of the viscosity of the patient's circulating blood versus a range of shear rates and FIG. 10B depicts a logarithmic depiction of viscosity versus shear rate. It should be understood that the curves depicted in those graphs are identical mathematically and that theDRSC viscometer920 disclosed above ensures greater accuracy than existing technology.

A combined handle/filter assembly (not shown) could be used at the top of the riser tubes R1 and R2. This assembly permits the introduction of an inert gas at atmospheric pressure into the riser tubes R1 and R2 above the respective column of fluids. In addition, this assembly acts as a handle for the insertion and removal of the blood receiving means22 when a disposable blood receiving means22 is utilized.

It should also be understood that the locations of many of the components in the blood receiving means22 are shown by way of example only and not by way of limitation. For example, the capillary52 can be positioned horizontally or vertically; thevalve mechanism46 does not necessarily have to be located at the elbow portions5A/50B of the riser tubes R1 and R2. It is within the broadest scope of the invention to include various locations of the components within the blood receiving means22 without deviating from the invention. In fact, the next embodiment discussed below utilizes such various locations.

In FIGS. 13-21, there is shown a morepreferred embodiment1020 of the DRSC viscometer described heretofore. Thissecond embodiment1020 for all intents and purposes is the same as thefirst embodiment920 except for the location of thevalve mechanism46, the use of avacutainer mechanism101, the position of thecapillary tube52 and the requisite volume of blood that is used in the blood receiving means. As a result, the equations (i.e., Equations 1-7) governing the operation of thissecond embodiment1020 and the plots concerning the column levels' time response and viscosity (i.e., FIGS. 6,10A and10B) are similar and will not be repeated here. Thus, the common details of the construction and operation ofembodiment1020 will not be reiterated. Furthermore, as stated previously with respect to theembodiment920, thecapillary tube52 used in theembodiment1020 does not necessarily have to be an elongated tube but may comprise a variety of configurations such as a coiled capillary tube.

As can be seen in FIG. 13, theembodiment1020 comprises a blood receivinglow means122 and the analyzer/output portion1024. As with the blood receiving means22 described earlier, the blood receiving means122 can be disposable or re-usable. As an example of a disposable blood receiving means122, a friction-type fitting147 (see FIG. 14) releasably secures the top end of riser tube R2 into thehousing60 while thevalve mechanism46 is friction-fitted at the top of the riser tube R1 into thehousing60. Thus, to remove the disposable blood receiving means122, the operator need only disengage the fitting147 and thevalve mechanism46 friction fit.

The blood receiving means122 comprises thevalve mechanism46 that is now located at the top of riser tube R1 and thecapillary tube52 has been located between the two riser tubes R1 and R2. In addition, avacutainer mechanism101 has been added to the blood receiving means122. Thevacutainer mechanism101 permits the retrieval of a sample of the first blood to reach the blood receiving means122 for subsequent blood analysis (e.g., hematocrit studies). However, it should be understood that thevacutainer mechanism101 does not form any part of the viscosity determination and does not impede, in any way, the operation of theDRSC viscometer1020 in determining blood viscosity according to that described with respect to theembodiment920. In fact, thevacutainer mechanism101, as will be described below, disengages from thevalve mechanism46 before the viscosity test run begins.

Thevacutainer mechanism101 comprisesvacutainer107 that is positionable by avacutainer driver109. Operation of thevacutainer mechanism101 is depicted in FIGS. 15,16,17A-17B and flowcharts FIG. 19A-19B. In particular, as shown most clearly in FIG. 17A, when the detector103 (e.g., a photodetector, photo-eye, etc.) detects the first or initial portion of the input blood from the patient (via the CBCM26), thedetector103 alerts themicroprocessor58 which activates thevacutainer driver109 to drive thevacutainer107 towards the puncturing means111 (e.g., needle, FIG. 15) on thevalve mechanism46 which punctures a piercable surface of thevacutainer107. Simultaneously, theprocessor58 commands thevalve driver86 to place the valve in the first position (as shown in FIG.17A). As a result, the first or initial portion of the input blood flow is captured in thevacutainer107. After a fixed time, to has elapsed, theprocessor58 commands thevacutainer driver109 to disengage thevacutainer107 from the puncturing means111. With this initial portion of the input blood flow captured in thevacutainer107, the operator can remove thevacutainer107 from thedriver109 and then presented to a separate analyzing mechanism either on-site or remotely-located.

Simultaneous with theprocessor58 commanding thevacutainer driver109 to disengage thevacutainer107 from the puncturing means111, theprocessor58 also commands thevalve driver86 to move the valve into the second position (FIG.17B). As a result, the input blood flow enters into the top of the riser tube R2, down the riser tube R2, through the capillary52 and up into riser tube R1. Thecolumn level detector56 monitors the rising blood column in riser tube R2. Whencolumn level detector56 detects a predetermined level, h_sv, it informs theprocessor58. The h_svis an exact value that corresponds to an exact volume of blood such that when the column of blood in riser tube R2 reaches h_2i, (FIGS.17B and17C), the column of blood in riser R1 will be at h_1i. Therefore, whencolumn level detector56 detects that h_svhas been reached, theprocessor58 activates thevalve driver86 to rotate the valve into the third position (FIG.17C), thereby isolating the two columns of blood from the input blood flow while simultaneously beginning the viscosity test run. This viscosity test run is similar to that described earlier with respect toembodiment920 and, as such, will not be repeated here.

Alternatively, as mentioned earlier, thecolumn level detector56 can be used to detect the falling column of blood in the first riser tube R1 and thesingle point detector954 can be used to detect the predetermined level, h_sv, of the rising column of blood in riser tube R2. Thus, it is within the broadest scope of the invention to cover the use of one column level detector for monitoring the change in position of the blood column in one riser tube and the use of a single point detector for detecting a single point of the blood column in the other riser tube.

It should be understood that any one point of the blood column can be detected by thesingle point detector954. The preferred point is the initial column level for the viscosity test run, namely h_1ior h_sv. However, any other point in the column can be detected in order to generate the corresponding height vs. time data/curve.

One exemplary implementation of the blood receiving means122 is shown in FIGS. 20-21. In particular, the riser tubes R1 and R2 (e.g., injection-molded pieces) haveintegral elbows50A and50B that are inserted into respective ends of acapillary element153. In particular, each end of thecapillary element153 forms a form fitting sleeve that slides over each end of theelbows50A and50B. As shown most clearly in FIG. 21, thecapillary element153 comprises a taperedentry port155 and atapered exit port157 to minimize any turbulence as the circulating blood passes from the end of theelbow50A into thecapillary element153 and then into theelbow50B and up into riser tube R2.

It should be pointed out that the “blood receiving” means of all embodiments disclosed herein are merely exemplary of various combinations of components, such as riser tubes, etc., which can take various other forms than those specifically disclosed herein.

As shown in FIG. 18, it is within the broadest scope of the invention to include any means and/or method for monitoring the movement of either one of the columns ofblood82/84 in the riser tubes R1/R2 and for detecting the single point in the other one of the columns and, as such, are not limited to theLED array64/CCD66 arrangement for thecolumn level detector56, nor to theLED964/photodetector966 arrangement for thesingle point detector954. In fact, the following type of physical detections (indicated by “SENSOR” in FIG. 8) are covered by the present invention:

d(Weight)/dt: the change in weight of either column of fluid with respect to time using a weight detecting means for each column of fluid as the sensor; e.g., w₁(t)−w₂(t);

d(Pressure)/dt: the change in pressure of either column of fluid with respect to time using a pressure transducer located at the top of each column of fluid; e.g., p₁(t)−p₂(t);

time of flight: the length of time it takes an acoustic signal to be emitted from a sensor (e.g., ultrasonic) located above either column of fluid and to be reflected and return to the sensor; e.g., time of flight₁(t)−time of flight₂(t);

d(Volume)/dt: the change in volume of either column of fluid with respect to time; e.g., V₁(t)−V₂(t);

d(Position)/dt: the change in position of either column level using a digital video camera; e.g., Pos₁(t)−Pos₂(t);

d(Mass)/dt: the change in mass with respect to time for either column of fluid; e.g., m₁(t)−m₂(t).

TheCCD66 may be any conventional device. One particularly suitable one is available from ScanVision Inc. of San Jose, Calif. That CCD is of 300 dpi- 83μ pixel resolution. The ScanVision Inc. CCD utilizes conventional CCD acquisition software. TheLED arrays64 can be implemented with a variety of light sources, including fiber optic lines.

Furthermore, thedoor76 of thehousing60 can be configured to be hinged along the bottom of thehousing60 so as to swing down in order to gain access to the blood receiving means22 or122.

It should be understood that it is within the broadest scope of theinvention920 and1020 to include auxiliary pressure (e.g., a pressure source such as a pump) as the motive force for moving the columns ofblood82/84 during the test run, as opposed to venting each of the riser tubes R1 and R2 to the ambient atmosphere.

It should be further understood that although thedisplay28 provides an efficient means for conveying the viscosity data to the user, the broadest scope of theDRSC viscometers920 and1020 does not require thedisplay28. Rather, as long as the viscosity data is available to any output means30, the objectives of the present invention are met. Furthermore, it should be understood that the analyzer/output portion924 inembodiments920 and1020 can accomplished by a any laptop personal computer and is not limited in any way by that which is depicted in FIGS. 2-3.

The blood receiving means22 and122 of therespective embodiments920 and1020 are typically located to be at a position that is lower than the patient's heart. By doing this, gravity assists the venous pressure in conveying the circulating blood to the blood receiving means22/122, but this also prevents any backflow of blood into the patient during the preliminary hook up and viscosity test run.

It should be understood that where a re-usable blood receiving means22 is used inembodiment920, or where a re-usable blood receiving means122 is used inembodiment1020, the step “insert disposable set” in FIG.9B and FIG. 19B, respectively, is omitted.

It should also be noted that, as mentioned earlier, the preferred method/means is to monitor the rising column ofblood84 with thecolumn level detector56 as opposed to monitoring the falling column ofblood82 because a large amount of noise is encountered when the fallingcolumn82 is monitored. The risingcolumn84 presents a more clean monitoring signal and is thus the preferred column to be monitored. However, it is within the broadest scope of this invention to include means for filtering or compensating this noise when the falling column is monitored by thecolumn level detector56.

Without further elaboration, the foregoing will so fully illustrate our invention and others may, by applying current or future knowledge, readily adapt the same for use under various conditions of service.

Claims (104)

We claim:

1. An apparatus for effecting the viscosity measurement of circulating blood in a living being, said apparatus comprising:

a lumen arranged to be coupled to the vascular system of the being;

a pair of tubes having respective first ends coupled to said lumen for receipt of circulating blood from the being, one of said pair of tubes comprising a capillary tube having some known parameters;

a valve for controlling the flow of circulating blood from the being's vascular system to said pair of tubes; and

an analyzer, coupled to said valve, for controlling said valve to permit the flow of blood into said pair of tubes whereupon the blood in each of said pair of tubes assumes a respective initial position with respect thereto, said analyzer also being arranged for operating said valve to isolate said pair of tubes from the being's vascular system and for coupling said pair of tubes together so that the position of the blood in said pair of tubes changes, said analyzer also being arranged for monitoring the blood position change in one of said tubes and detecting a single blood position in the other one of said pair of tubes and calculating the viscosity of the blood based thereon.

2. The apparatus ofclaim 1 wherein said apparatus is adapted for effecting the viscosity measurement of circulating blood of a living being in real-time.

3. The apparatus ofclaim 2 wherein each of said tubes has a second end and whereupon said apparatus additionally comprises means for venting said second ends of said pair of tubes to the ambient atmosphere.

4. The apparatus ofclaim 2 wherein said analyzer detects the change in weight of one of said pair of tubes over time to effect said monitoring of the blood position change.

5. The apparatus ofclaim 2 wherein said respective initial positions comprise a first pre-test position of a first column of blood with respect to one of said pair of tubes and a second pre-test position of a second column of blood with respect to the other of said pair of tubes, said first pre-test position and said second pre-test position being different from each other.

6. The apparatus ofclaim 5 wherein said pair of tubes are oriented upright and wherein said first pre-test position comprises a first initial height of said first column of blood and said second pre-test position comprises a second initial height of said second column of blood.

7. The apparatus ofclaim 6 wherein said analyzer detects the change in column height of one of said first and second columns of blood.

8. The apparatus ofclaim 7 wherein said analyzer detects said change in column height by detecting the time of flight of emitted signals toward the top of one of said columns.

9. The apparatus ofclaim 8 wherein said emitted signals are acoustic signals.

10. The apparatus ofclaim 6 wherein said analyzer includes a digital video camera for detecting the change in column height of one of said first and second columns of blood.

11. The apparatus ofclaim 6 wherein said analyzer detects the change in pressure of one of said first and second columns of blood over time to effect said monitoring of the blood position change.

12. The apparatus ofclaim 2 wherein said analyzer detects the change of volume in blood of one of said pair of tubes to effect said monitoring of the blood position change.

13. The apparatus ofclaim 2 further comprising environmental control means, said environmental control means maintaining the blood in said capillary tube at substantially the same temperature of the living being during the time said analyzer couples said pair of tubes together.

14. The apparatus ofclaim 13 wherein said environmental control means maintains the blood in said pair of tubes at substantially the same temperature of the living being during the time said analyzer couples said pair of tubes together.

15. The apparatus ofclaim 5 wherein said respective initial positions of the blood in said pair of tubes is established by the operation of said analyzer.

16. The apparatus ofclaim 6 wherein said first initial height and said second initial height are established by the operation of said analyzer.

17. The apparatus ofclaim 5 wherein said position of the blood in said pair of tubes changes comprises the movement of a respective level of said first and second columns of blood moving in opposite directions and wherein said analyzer determines the difference value between said respective levels.

18. The apparatus ofclaim 6 wherein said position of the blood in said pair of tubes changes comprises a falling column of blood away from said first initial height and a rising column of blood away from said second initial height, said analyzer monitoring the blood position change of said rising column of blood and detecting said single blood position from said falling column of blood.

19. The apparatus ofclaim 18 wherein said single blood position is said first initial height.

20. The apparatus ofclaim 19 wherein said analyzer determines the difference values of said heights of said columns of blood over time, known as h₁(t)−h₂(t) wherein h₁(t) is said height of said falling column of blood and h₂(t) is said height of said rising column of blood.

21. The apparatus ofclaim 20 wherein said analyzer determines an offset of said heights of said columns of blood, known as Δh, after monitoring the blood position change in said rising column of blood for a period of time and from said single blood position from said falling column of blood.

22. The apparatus ofclaim 21 wherein said analyzer calculates the viscosity using h₁(t)−h₂(t) and Δh to determine the consistency index, k, and the power law index, n, as given by:$h_1\left(t\right)-h_2\left(t\right)-\Delta h=-{\left\{\left(\frac{n-1}{n}\right)\alpha t+{\left(\Delta h-h_0\right)}^{\frac{n-1}{n}}\right\}}^{\frac{n}{n-1}}$

where$\alpha =-\frac{1}{2}{\left(\frac{4{\mathrm{kL}}_c}{\rho g{\phi }_c}\right)}^n\left(\frac{n}{3n+1}\right)\left(\frac{{\phi }_c^3}{{\phi }_r^2}\right)$

and where

h₀=h₁(0)-h₂(0);

L_c=length of capillary tube;

φ_c=inside diameter of said capillary tube

φ_r=diameter of said columns of blood and where φ_c<<<φ_r

ρ=blood fluid density;

g=gravitational constant.

23. The apparatus ofclaim 22 wherein said analyzer calculates the viscosity, μ, using said determined values of n and k in the equation:

μ=k|{dot over (γ)}|ⁿ⁻¹

where$\stackrel{.}{\gamma }=\left(\frac{3n+1}{n}\right)\frac{8Q}{{\mathrm{\pi \phi }}_c^3}$

and where

Q=volumetric flow rate in said capillary tube

φ_c=capillary tube diameter; and

{dot over (γ)}=shear rate.

24. The apparatus ofclaim 2 wherein said analyzer operates said valve to isolate said pair of tubes from the living being's vascular system while simultaneously coupling said pair of tubes together.

25. The apparatus ofclaim 2 wherein said analyzer comprises a single monitor for one of said pair of tubes, said monitor monitoring the blood position change in said one of said pair of tubes.

26. The apparatus ofclaim 25 wherein said monitor comprises a light array and a charge coupled device (CCD).

27. The apparatus ofclaim 26 wherein said light array comprises a plurality of light emitting diodes arranged in linear fashion to illuminate said one of said pair of tubes along the length of said tube.

28. The apparatus ofclaim 2 wherein said analyzer comprises a detector for detecting said single blood position.

29. The apparatus ofclaim 28 wherein said detector comprises a light emitting diode and a photodetector.

30. The apparatus ofclaim 2 wherein said pair of tubes is disposable.

31. The apparatus ofclaim 2 wherein said valve mechanism is disposable.

32. A method for determining the viscosity of circulating blood of a living being, said method comprising the steps of:

(a) providing access to the circulating blood of the living being to form an input flow of circulating blood;

(b) dividing said input flow of circulating blood into a first flow path and a second flow path into which respective portions of said input flow pass, one of said first or second flow paths including a passageway portion having some known parameters;

(c) isolating said first and second flow paths from said input flow and coupling said first and second flow paths together so that the position of the blood in each of said flow paths changes;

(d) monitoring the blood position change in one of said first and second flow paths over time;

(e) detecting a single blood position in the other one of said first and second flow paths; and

(f) calculating the viscosity of said circulating blood based on said blood position change, said single blood position and on selected known parameters of said passageway portion.

33. The method ofclaim 32 wherein said step of calculating the viscosity of said circulating blood is conducted in real-time.

34. The method ofclaim 33 wherein said first and second flow paths comprise respective columns of blood in upright positions and said step of monitoring the blood position change over time comprises monitoring the change in column height of one of said first and second columns of blood over time.

35. The method ofclaim 34 wherein said step of detecting a single blood position in the other one of said first and second flow paths comprises detecting a single column height.

36. The method ofclaim 34 wherein said first and second columns are vented to ambient atmosphere.

37. The method ofclaim 33 wherein said first and second flow paths comprise respective columns in upright positions and said step of monitoring the blood position change over time comprises monitoring the change in weight of one of said first and second columns of circulating blood over time.

38. The method ofclaim 33 wherein said first and second flow paths comprise respective columns in upright positions and said step of monitoring the blood position change over time comprises monitoring the time of flight of emitted signals towards the top of one of said columns.

39. The method ofclaim 38 wherein said emitted signals are acoustic signals.

40. The method ofclaim 34 wherein said column height is monitored by a digital video camera.

41. The method ofclaim 33 wherein said first and second flow paths comprise respective columns in upright positions and said step of monitoring the blood position change over time comprises monitoring the change in pressure of one of said first and second columns of blood over time.

42. The method ofclaim 33 wherein said first and second flow paths comprise respective columns in upright positions and said step of monitoring the blood position change over time comprises monitoring the change in mass of one of said first and second columns of circulating blood over time.

43. The method ofclaim 33 wherein said first and second flow paths comprise respective columns in upright positions and said step of monitoring the blood position change over time comprises monitoring the change in volume of one of said first and second columns of blood over time.

44. The method ofclaim 33 further comprising the step of maintaining the temperature of said passageway portion at substantially the same temperature of the living being during said step of monitoring the blood position change in one of said first and said flow paths.

45. The method ofclaim 44 wherein said step of maintaining the temperature further comprises maintaining the temperature of said first and second flow paths at substantially the same temperature of the living being during said step of monitoring the blood position change in one of said first and said flow paths.

46. The method ofclaim 34 wherein said step of dividing said input flow of circulating blood into a first flow path and a second flow path comprises establishing a first pre-test level for said first column of blood and a second pre-test level for said second column of blood, said first and second pre-test levels being different from each other.

47. The method ofclaim 46 wherein said step of calculating the viscosity comprises determining difference values of said heights of said first and second columns of fluid over time, known as h₁(t)−h₂(t) wherein h, is said height of said first column and h₂is said height of said second column.

48. The method ofclaim 47 wherein said step of calculating the viscosity further comprises detecting an offset of said heights of said first and second columns, known as Δh.

49. The method ofclaim 48 wherein said step of calculating the viscosity further comprises using h₁(t)−h₂(t) and Δh to determine the consistency index, k, and the power law index, n, as given by:$h_1\left(t\right)-h_2\left(t\right)-\Delta h=-{\left\{\left(\frac{n-1}{n}\right)\alpha t+{\left(\Delta h-h_0\right)}^{\frac{n-1}{n}}\right\}}^{\frac{n}{n-1}}$

where$\alpha =-\frac{1}{2}{\left(\frac{4{\mathrm{kL}}_c}{\rho g{\phi }_c}\right)}^n\left(\frac{n}{3n+1}\right)\left(\frac{{\phi }_c^3}{{\phi }_r^2}\right)$

and where

h₀=h₁(0)-h₂(0);

L_c=length of said passageway portion;

φ_c=inside diameter of said passageway portion;

φ_r=diameter of said first or second column of fluid and where d_c<<<d_r

ρ=blood fluid density;

g=gravitational constant.

50. The method ofclaim 49 wherein said step of calculating the viscosity, μ, further comprises using the determined values of n and k in the equation:

μ=k|{dot over (γ)}|ⁿ⁻¹

where$\stackrel{.}{\gamma }=\left(\frac{3n+1}{n}\right)\frac{8Q}{{\mathrm{\pi \phi }}_c^3}$

and where

Q=volumetric flow rate in said passageway portion

φ_c=passageway portion diameter; and

{dot over (γ)}=shear rate.

51. An apparatus for effecting the viscosity measurement of circulating blood in a living being, said apparatus comprising:

a lumen arranged to be coupled to the vascular system of the being;

a pair of tubes having respective first ends and second ends, said first ends being coupled together via a capillary tube having some known parameters;

a valve for controlling the flow of circulating blood from the being's vascular system to said pair of tubes, said valve being coupled to a second end of one of said pair of tubes and being coupled to said lumen; and

an analyzer, coupled to said valve, for controlling said valve to permit the flow of blood into said pair of tubes whereupon the blood in each of said pair of tubes assumes a respective initial position with respect thereto, said analyzer also being arranged for operating said valve to isolate said pair of tubes from the being's vascular system so that the position of the blood in said pair of tubes changes, said analyzer also being arranged for monitoring the blood position change in one of said tubes and detecting a single blood position in the other one of said pair of tubes and calculating the viscosity of the blood based thereon.

52. The apparatus ofclaim 51 wherein said apparatus is adapted for effecting the viscosity measurement of circulating blood of a living being in real-time.

53. The apparatus ofclaim 52 further comprises means for venting said second end of said other one of said pair of tubes to atmosphere.

54. The apparatus ofclaim 52 wherein said analyzer detects the change in weight of one of said pair of tubes over time to effect said monitoring of the blood position change.

55. The apparatus ofclaim 52 wherein said respective initial positions comprise a first pre-test position of a first column of blood with respect to one of said pair of tubes and a second pre-test position of a second column of blood with respect to the other of said pair of tubes, said first pre-test position and said second pre-test position being different from each other.

56. The apparatus ofclaim 55 wherein said pair of tubes are oriented upright and wherein said first pre-test position comprises a first initial height of said first column of blood and said second pre-test position comprises a second initial height of said second column of blood.

57. The apparatus ofclaim 56 wherein said analyzer detects the change in column height of one of said first and second columns of blood.

58. The apparatus ofclaim 57 wherein said analyzer detects said change in column height by detecting the time of flight of emitted signals toward the top of one of said columns.

59. The apparatus ofclaim 58 wherein said emitted signals are acoustic signals.

60. The apparatus ofclaim 56 wherein said analyzer includes a digital video camera for detecting the change in column height of one of said first and second columns of blood.

61. The apparatus ofclaim 56 wherein said analyzer detects the change in pressure of one of said first and second columns of blood over time to effect said monitoring of the blood position change.

62. The apparatus ofclaim 52 wherein said analyzer detects the change of volume in blood of one of said pair of tubes to effect said monitoring of the blood position change.

63. The apparatus ofclaim 52 further comprising environmental control means, said environmental control means maintaining the blood in said capillary tube at substantially the same temperature of the living being during the time said analyzer couples said pair of tubes together.

64. The apparatus ofclaim 63 wherein said environmental control means maintains the blood in said pair of tubes at substantially the same temperature of the living being during the time said analyzer couples said pair of tubes together.

65. The apparatus ofclaim 55 wherein said respective initial positions of the blood in said pair of tubes is established by the operation of said analyzer.

66. The apparatus ofclaim 56 wherein said first initial height and said second initial height are established by the operation of said analyzer.

67. The apparatus ofclaim 55 wherein said position of the blood in said pair of tubes changes comprises the movement of a respective level of said first and second columns of blood moving in opposite directions and wherein said analyzer determines the difference value between said respective levels.

68. The apparatus ofclaim 56 wherein said position of the blood in said pair of tubes changes comprises a falling column of blood away from said first initial height and a rising column of blood away from said second initial height, said analyzer monitoring the blood position change of said rising column of blood and detecting said single blood position from said falling column of blood.

69. The apparatus ofclaim 68 wherein said single blood position is said first initial height.

70. The apparatus ofclaim 56 wherein said analyzer determines the difference values of said heights of said columns of blood over time, known as h₁(t)−h₂(t) wherein h₁(t) is said height of said first column of blood and h₂(t) is said height of said second column of blood.

71. The apparatus ofclaim 58 wherein said analyzer detects an offset of said heights of said columns of blood, known as Δh, after monitoring the blood position change for a period of time.

72. The apparatus ofclaim 71 wherein said analyzer calculates the viscosity using h₁(t)−h₂(t) and Δh to determine the consistency index, k, and the power law index, n, as given by:$h_1\left(t\right)-h_2\left(t\right)-\Delta h=-{\left\{\left(\frac{n-1}{n}\right)\alpha t+{\left(\Delta h-h_0\right)}^{\frac{n-1}{n}}\right\}}^{\frac{n}{n-1}}$

where$\alpha =-\frac{1}{2}{\left(\frac{4{\mathrm{kL}}_c}{\rho g{\phi }_c}\right)}^n\left(\frac{n}{3n+1}\right)\left(\frac{{\phi }_c^3}{{\phi }_r^2}\right)$

and where

h₀=h₁(0)-h₂(0);

L_c=length of capillary tube;

φ_c=inside diameter of said capillary tube

φ_r=diameter of said columns of blood and where d_c<<<d_r

ρ=blood fluid density;

g=gravitational constant.

73. The apparatus ofclaim 72 wherein said analyzer calculates the viscosity, μ, using said determined values of n and k in the equation:

μ=k|{dot over (γ)}|ⁿ⁻¹

where$\stackrel{.}{\gamma }=\left(\frac{3n+1}{n}\right)\frac{8Q}{{\mathrm{\pi \phi }}_c^3}$

and where

Q=volumetric flow rate in said capillary tube

φ_c=capillary tube diameter; and

{dot over (γ)}=shear rate.

74. The apparatus ofclaim 52 wherein said analyzer comprises a monitor for one of said pair of tubes, said monitor monitoring the blood position change in said one of said pair of tubes.

75. The apparatus ofclaim 74 wherein said monitor comprises a light array and a charge coupled device (CCD).

76. The apparatus ofclaim 75 wherein said light array comprises a plurality of light emitting diodes arranged in linear fashion to illuminate said tube along the length of said tube.

77. The apparatus ofclaim 52 wherein said analyzer comprises a detector for detecting said single blood position.

78. The apparatus ofclaim 77 wherein said detector comprises a light emitting diode and a photodetector.

79. The apparatus ofclaim 52 wherein said pair of tubes is disposable.

80. The apparatus ofclaim 52 wherein said valve mechanism is disposable.

81. The apparatus ofclaim 51 wherein said analyzer further comprises a container, said container collecting an initial portion of the flow of circulating blood from the being's vascular system.

82. The apparatus ofclaim 81 wherein said analyzer further comprises a detector adjacent an input port of said valve for detecting said initial portion of the flow of circulating blood from the being's vascular system.

83. The apparatus ofclaim 82 wherein said valve isolates said container from the being's vascular system while coupling said pair of tubes to the being's vascular system.

84. The apparatus ofclaim 74 wherein one of said respective monitors detects a predetermined level in one of said pair of tubes in order for said analyzer to isolate said pair of tubes from the being's vascular system.

85. A method for determining the viscosity of circulating blood of a living being, said method comprising the steps of:

(a) providing access to the circulating blood of the living being to form an input flow of circulating blood;

(b) directing said input flow into one end of a pair of tubes coupled together via a passageway having some known parameters, said input flow passing through a first one of said pair of tubes, through said passageway and into a first portion of a second one of said pair of tubes in order to form respective columns in said first and second tubes;

(c) isolating said respective columns from said input flow so that the position of the blood in each of said columns changes;

(d) monitoring the blood position change of one of said columns of blood over time;

(e) detecting a single blood position in the other one of said pair of tubes; and

(f) calculating the viscosity of the circulating blood based on said blood position change, said single blood position and on selected known parameters of said passageway.

86. The method ofclaim 85 wherein said step of calculating the viscosity of the circulating blood is conducted in real-time.

87. The method ofclaim 86 wherein said respective columns of blood are in upright positions and said step of monitoring the blood position change over time comprises monitoring the change in column height of one of said columns of blood over time.

88. The method ofclaim 87 wherein said step of detecting a single blood position in the other one of said pair of tubes comprises detecting a single column height.

89. The method ofclaim 87 wherein one end of said pair of tubes is vented to ambient atmosphere.

90. The method ofclaim 86 wherein said respective columns are in upright positions and said step of monitoring the blood position change over time comprises monitoring the change in weight of one of said columns of circulating blood over time.

91. The method ofclaim 86 wherein said respective columns are in upright positions and said step of monitoring the blood position change over time comprises monitoring the time of flight of emitted signals towards the top of one of said columns.

92. The method ofclaim 91 wherein said emitted signals are acoustic signals.

93. The method ofclaim 87 wherein said column height is monitored by a digital video camera.

94. The method ofclaim 86 wherein said columns are in upright positions and said step of monitoring the blood position change over time comprises monitoring the change in pressure of one of said columns of blood over time.

95. The method ofclaim 86 wherein said columns are in upright positions and said step of monitoring the blood position change over time comprises monitoring the change in mass of one of said columns of circulating blood over time.

96. The method ofclaim 86 wherein said columns are in upright positions and said step of monitoring the blood position change over time comprises monitoring the change in volume of one of said columns of blood over time.

97. The method ofclaim 86, further comprising the step of maintaining the temperature of said passageway at substantially the same temperature of the living being during said step of monitoring the blood position change in said respective columns.

98. The method ofclaim 97 wherein said step of maintaining the temperature further comprises maintaining the temperature of said respective columns at substantially the same temperature of the living being during said step of monitoring the blood position change in one of said columns.

99. The method ofclaim 87 wherein said step of directing said input flow of circulating blood into one end of a pair of tubes comprises establishing a first pre-test level for said first column of blood and a second pre-test level for said second column of blood, said first and second pre-test levels being different from each other.

100. The method ofclaim 99 wherein said step of calculating the viscosity comprises determining difference values of said heights of said first and second columns of fluid over time, known as h₁(t)−h₂(t) wherein h₁is said height of said first column and h₂is said height of said second column.

101. The method ofclaim 100 wherein said step of calculating the viscosity further comprises detecting an offset of said heights of said first and second columns, known as Δh.

102. The method ofclaim 101 wherein said step of calculating the viscosity further comprises using h₁(t)−h₂(t) and Δh to determine the consistency index, k, and the power law index, n, as given by:$h_1\left(t\right)-h_2\left(t\right)-\Delta h=-{\left\{\left(\frac{n-1}{n}\right)\alpha t+{\left(\Delta h-h_0\right)}^{\frac{n-1}{n}}\right\}}^{\frac{n}{n-1}}$

where$\alpha =-\frac{1}{2}{\left(\frac{4{\mathrm{kL}}_c}{\rho g{\phi }_c}\right)}^n\left(\frac{n}{3n+1}\right)\left(\frac{{\phi }_c^3}{{\phi }_r^2}\right)$

and where

h₀=h₁(0)-h₂(0);

L_c=length of passageway;

φ_c=inside diameter of said passageway

φ_r=diameter of said first or second column of fluid and where d_c<<<d_r

ρ=blood fluid density;

g=gravitational constant.

103. The method ofclaim 102 wherein said step of calculating the viscosity, μ, further comprises using the determined values of n and k in the equation:

μ=k|{dot over (γ)}|ⁿ⁻¹

where$\stackrel{.}{\gamma }=\left(\frac{3n+1}{n}\right)\frac{8Q}{{\mathrm{\pi \phi }}_c^3}$

and where

Q=volumetric flow rate in said passageway

φ_c=passageway diameter; and

{dot over (γ)}shear rate.

104. The method ofclaim 85 wherein said step of providing access to the circulating blood of the living being comprises collecting a finite amount of the initial portion of said input flow of circulating blood into a container.

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